1. Field of the Invention
The present invention relates to methods and apparatus for fabricating continuous length conveyor belting. More particularly, the present invention is directed to methods and apparatus for fabricating belting having undulated flexible side walls.
2. The Prior Art
Conveyor belts are widely used for moving various materials from one location to another. In its simplest form, a conveyor belt is comprised of a flat belt secured end-to-end so as to form an elongated loop, and is used by being passed around a pair of rollers located at the ends of the elongated loop, and with intermediate supporting rollers or side plates situated therebetween. Being fabricated from a lamination of fabric and rubber (or a rubber-like material), a typical flat conveyor belt is capable of sustained operation before substantial degradation occurs.
Simple flat conveyor belts are adequate for moving large or packaged materials, and when used in a trough-like configuration or provided with side flanges which protrude upwardly from the body of the belt so as to serve as side walls, they may be used to move a large variety of bulk materials, since the trough configuration or side walls will prevent bulk materials from sliding off the edges of the belt. When it is desired to elevate bulk materials, it is often necessary to further provide a flat belt with either cleats or nubs to prevent the material from sliding back down the belt as it is conveyed.
It has been found possible to utilize a simple straight side wall in applications where a relatively low wall is all that is required to prevent the bulk materials from sliding off the edges of the belt, but even when a very resilient material is utilized to fabricate a high straight side wall (e.g., above about two inches high), the substantial stress applied to the upper portions of such high walls as they pass around the end rollers of a conveyor assembly results in rapid degradation of the belt.
To avoid these limitations, it has become increasingly common to provide conveyor belts with side walls having a sinusoidal or other non-linear shape. These undulated side walls relieve the stress on the wall as the belt passes around the rollers. Adjustment of the spacing between undulations and adjustment of the magnitude of the undulations allows virtually any height of side-wall to be utilized without concern over premature failure of the side wall material.
Conveyor belts are made by laminating raw stock material (e.g., natural rubber, black sytrene-butadiene rubber, neoprene, nitrile, or other synthetic material, hereinafter referred to generally as "rubber stock", or sometimes simply "stock") with layers of a suitable fabric so as to meet a desired specification of tensile strength, and the like. The formed belt is then cured under conditions of heat and pressure sufficient to cause vulcanization.
In the past, when it has been desired to add low straight side walls, it has been found advantageous to prepare raw side walls and place them in a recess in the belt mold so that each component is cured together with the conveyor belt. The substantial heat and pressure utilized to cure the raw material results in substantial homogeneity between the side walls and the conveyor belt to which they are secured. This simultaneous curing results in a much stronger bond between the belt and side walls than is obtainable if already cured side walls are secured to cured belting by use of adhesives or a purely thermal process.
Unfortunately, it has not proven feasible to produce conveyor belts having undulated or other non-linear side walls using existing technology so as to simultaneously cure the side walls and the belt. Rather, current technology involves the multiple steps of (1) curing the required length of flat belt; (2) placing straight rubber side wall stock into a mold to form it into the desired undulated pattern; (3) curing the raw undulated side wall stock; (4) cleaning and buffing those areas of the flat belt and the undulated wall that are to be secured together; and (5) applying adhesive so as to bond the undulated wall to the flat belt.
The result of this approach for fabricating undulated side wall conveyor belts has been that after some period of use, although the belt and undulated side wall material might still be in excellent condition, it is not uncommon for the undulated side wall to become delaminated from the belt due to failure of the bonding process. This condition results in equipment downtime while the belt is repaired or replaced, and also results in increased maintenance and inventory expenses.
In view of the foregoing it will be appreciated that it would be a significant advancement in the field of conveyor belt fabrication if methods and apparatus could be provided that would permit the simultaneous curing of raw non-linear side walls with raw belt material so as to successfully avoid the aforementioned problems.